M. Fathi, S. Hickel, D. Roekaerts (2025)
Combustion and Flame 281: 114360. doi: 10.1016/j.combustflame.2025.114360
This work introduces a modeling technique for the use of transcritical counterflow flames in flamelet modeling, expanding the capabilities of large-eddy simulations with multiphase thermodynamics (LES-MT) to accurately modeling transcritical combustion. By incorporating real-fluid effects and two-phase interactions, the transcritical flamelet library provides a high-fidelity representation of the complex behaviors in high-pressure multiphase autoignition scenarios. This calibration-free approach can significantly improve our understanding of the transcritical combustion of emerging fuels such as OME3 or their combination with traditional fuels such as n-dodecane.
We present a new method for high-fidelity simulations of transcritical combustion using a real-fluid multiphase thermo-transport solver based on the LES-MT framework with a transcritical flamelet library. This model effectively combines detailed chemical kinetics with multiphase interactions in complex fuel sprays. Validation against experimental data for Spray-A with n-dodecane fueling confirms the accuracy of the LES-MT approach in predicting ignition delay time, vapor penetration length, and liquid penetration length under transcritical conditions.
LES-MT results indicate distinct differences in the behaviors of transcritical evaporation, ignition, and soot formation between the injection of pure n-dodecane, pure OME3, and a nC12– OME3 fuel mixture. Adding OME3 to nC12 shortens the two-phase region and reduces the lift-off length of the cool flame, resulting in earlier ignition. Although OME3 shows an advantage in being nearly soot-free, the mixed fuel case shows a surprisingly modest reduction of soot formation due to fuel-rich conditions and reduced oxygen availability, driven by OME3’s faster evaporation. These findings, based on the proposed reduced hybrid reaction mechanism, underscore the need for further studies to fully understand the complex interactions in mixed fuels under varying conditions.
